Interpretive Summary: More than a 100,000 ha of the Westside of the San Joaquin Valley (SJV) in California are impacted by saline soils and shallow, saline water tables. Severe restrictions on drain water disposal in recent years, combined with decreased imported irrigation water supplies has accelerated interest in finding salt tolerant crops that are more profitable than cotton. Pistachios have been grown in some of these areas for almost 30 years but always with low salinity (< 1 dS/m) irrigation water. The objective of this trial was to assess the production-scale sustainability and profitability of developing young pistachios using saline groundwater inter-planted with cotton and irrigated with drip tape. Large-scale commercial production of cotton and development of pistachios was unaffected by salinity for the first two years at an irrigation water EC of 5.4 dS/m and B concentration of 11 mg/L. General growth of pistachio trees and the development of the young Kerman scaffolds were unaffected by saline irrigation treatments, indicating that long-term management of pistachio trees using saline water and drip irrigation may be easier than cultivation of cotton and management of seedbed salinity.

Technical Abstract:
Cotton has long been considered a salt tolerant crop, but despite many small-scale field trials over 30 years almost no marginally saline water in the San Joaquin Valley of California is used for commercial-scale production. Over this same period water costs have increased four to tenfold, cotton prices have stagnated and more than 100,000 ha have been converted to pistachios. Work in Iran, salt tank studies at the USDA Salinity Laboratory in Riverside, CA, and a small plot study in the southern San Joaquin Valley indicate pistachios may tolerate soil extract salinity (ECe) of up to 9.4 dS/m, but this has not been proven on a commercial scale in California. Such a trial was established in 2004, using 7.9 ha test plots over two 62.7 ha fields to test the use of saline irrigation water for development of a new pistachio orchard inter-planted with cotton using shallow subsurface drip tape. Cotton yield and pistachio development were unaffected by salinity for the first two years of this trial at an irrigation water EC of 5.4 dS/m and B concentration of 11 mg/L. Average soil salinity doubled by the end of the first season under saline irrigation compared to fresh water (EC = 0.5 dS/m), but was sufficiently reduced by 250 mm of winter leaching and spring cotton germination irrigation with fresh water to prevent adverse impacts the second year. However, early season stand establishment and growth of cotton in the third year (2006) was reduced for the saline well treatment compared to fresh water irrigation despite application of 450 mm of fresh water for leaching/germination to all plots. Pistachio shoot growth and increase in rootstock girth for this second year after planting was unaffected.